The present invention relates to an image reading device which optically reads a text image by moving an image reading unit on which a line sensor and a light source for text illuminating is mounted. More specifically, it relates to a mechanism which holds the image reading unit such that it cannot move when time device is transported.
The present invention also relates to an image reading device which reads a text image by moving an image reading unit. More specifically, it relates to the structure of a reducing or magnifying optical system with which the image reading unit is provided.
The present invention further relates to an image reading device which continuously reads a transparent text such as a photographic film, and outputs the data as an image signal.
FIG. 47 is a perspective view which schematically shows a mechanism for holding a reading unit when an image reading device is transported. As shown in the figure, in the conventional reading device, a reading unit 201 having a light source 201a or a line sensor (not shown in the figure) moves in a direction A or B along a guide shall 208 fixed to a frame 202 (A indicates a front side of the image reading device, and B indicates a rear side of the device). A screwhole 201b is formed a the rear surface of the reading unit: 201, and a throughhole 202a is formed in the frame 202 coaxially with the screwhole 201b. A stay 204 is fixed to the frame 202 by means of fixing screws 204a, and a throughhole 204b is formed in the stay 204 coaxially with the screwhole 201b in the reading unit 201 and the throughhole 202a in the frame 202. When the image reading device is transported, the reading unit 201 is fixed by screwing a retaining screw 205 having a thread 205a into the hole 201b via the throughhole 204b of the stay 204 and the throughhole 202a of the frame 202 so that the reading unit 201 cannot move with respect to the guide shaft 203, thereby preventing damage or distortion of the optical system.
FIG. 48 is a sectional view which schematically shows the structure of a reading unit 211 in another conventional image reading device. As shown in the figure, the reading unit 211 comprises a frame 212 that prevents intrusion of stray light from outside the device, and light sources 213 provided in the upper part of the frame for illuminating the text. The frame 212 contains fixed mirrors 217, 218, 219 that reflect light from a text 216 mounted on a glass plate 214 and clamped from above by a cover 215, a lens tube 220 made up of lenses, a fixed mirror 221 and a line sensor 222. In the reading unit 211 having the above construction, light L from the text 216 impinges on the lens tube 220 via the fixed mirrors 217, 218, 219, is made to converge by the lens tube 220, and forms an image via the fixed mirror 221 on the image-forming surface of the line sensor 222 where the image is converted to an electrical signal. As the reading unit 211 moves in a direction A, it reads image information on the text 216 one line at a time, converts it to an electrical signal, and outputs this signal to a printer, a display device or the like.
FIG. 49 is a perspective view showing a mechanism used for moving the optical parts which provide the reading unit in FIG. 48 with reducing or magnifying function, as is disclosed for example in Japanese Utility Model Kokoku Publication H5-16758 (16758/1993). As shown in FIG. 49, a wire rope 226 wound around a drive pulley 224 and a driven pulley 225, and a wire rope 229 wound around a drive pulley 227 and a driven pulley 228, are respectively attached to the two ends of a moving member 223 on which optical parts such as mirrors and a lens tube are mounted. The moving member 223 moves in the direction A or B by the rotational drive force of a motor 232 which is transmitted to a shaft 231 between the drive pulleys 224, 227 via a bell 230.
FIG. 50 to FIG. 56 are diagrams of another conventional image reading device. FIG. 50 and FIG. 51 are views in perspective, schematically showing the external appearance of the image reading device. FIG. 52 to FIG. 54 are diagrams showing the process of inserting a film in a film holder, and mounting it on a stage. FIG. 55 is a schematic view in section showing the construction of the drive part of the stage. FIG. 56 is a schematic view in section showing the construction of the optical system used for reading an image on a film.
In this image reading device, when a inserted, an illuminating part 243 is first raised as shown in FIG. 51; the film 242 is inserted in the film holder 244 so that one frame is in the window 244a of the holder 244 as shown in FIG. 52; the holder 244 is inserted in a stage 245 on a horizontal surface 241 as shown in FIG. 53; and the illuminating part 243 is then lowered to close it as shown in FIG. 54. When the stage 245 is moved in a slit 241a on the horizontal surface 241, the holder 244 and the film 242 which is gripped in the holder are displaced, and one frame of the film 242 is read.
The mechanism which displaces the stage 245 comprises a stepping motor 247 fixed to a base 246, a lead screw 249 connected to the stepping motor 247 via a joint 248 and a null 250 connected to the stage 245, this nut 250 screwing onto the lead screw 249 as shown in FIG. 55. The stage 245 is displaced in a direction G by driving the stepping motor 247. The optical system for reading an image on the film 242 comprises a lamp unit 251, a mirror 252, a lens unit 253 and a CCD line sensor 254 as shown in FIG. 56.
However, in the conventional image reading device shown in FIG. 47, there was a problem in that a screwdriver or other tool was required to attach or remove the retaining screw 205. Moreover, the retaining screw 205 had to be carefully kept after it was removed so that it was not lost, and after removing it, dust and dirt were liable to enter the image reading device through the throughholes 204b, 202a which were thereby left open.
Further, in the conventional image reading device shown in FIG. 48 and FIG. 49, if the drive pulleys 224, 227 and the wire ropes 226, 229 should slip or if the diameters of the drive pulleys 224, 227 or those of the wire ropes 226, 229 are slightly different, an error occurs in the displacement amount of the wire ropes 226, 229 so that the moving member 223 inclines at an angle .delta. to a reference line 233 perpendicular to the direction of motion. This world thereby give rise to distortion in the image reading by the line sensor.
Further, in the conventional image reading device shown in FIG. 50 to FIG. 56, when one frame on the film has been read and it is desired to read the next frame, the operator has to raise the illumination part 243, remove the holder 244 from the stage 245, insert the film 242 in the holder 244 so that the next frame is in the window 244a off the holder 244, re-insert the holder 244 in the stage 245, and then lower the illumination part 243. This sequence of operations was troublesome to perform, and took a great deal of time. In addition, the slit 241a had to be provided in the horizontal surface 241 to scan the film 242 while moving the stage 245 on the surface 241 of the image reading device. It was therefore difficult to make the image reading device compact, and in particular, if it was desired to enlarge the window of the holder 244 or increase the number of windows so that a plurality of frames of the film 242 could be read continuously, it was even more difficult to make the image reading device compact.